<template>
  <div class="liquid-effect">
    <canvas></canvas>
  </div>
</template>

<script>
// https://github.com/PavelDoGreat/WebGL-Fluid-Simulation
export default {
  name: "LiquidEffect",

  mounted() {
    this.init();
  },

  methods: {
    init() {
      var _createClass = (function () {
        function defineProperties(target, props) {
          for (var i = 0; i < props.length; i++) {
            var descriptor = props[i];
            descriptor.enumerable = descriptor.enumerable || false;
            descriptor.configurable = true;
            if ("value" in descriptor) descriptor.writable = true;
            Object.defineProperty(target, descriptor.key, descriptor);
          }
        }
        return function (Constructor, protoProps, staticProps) {
          if (protoProps) defineProperties(Constructor.prototype, protoProps);
          if (staticProps) defineProperties(Constructor, staticProps);
          return Constructor;
        };
      })();
      function _classCallCheck(instance, Constructor) {
        if (!(instance instanceof Constructor)) {
          throw new TypeError("Cannot call a class as a function");
        }
      }

      var canvas = document.getElementsByTagName("canvas")[0];
      canvas.width = canvas.clientWidth;
      canvas.height = canvas.clientHeight;

      var config = {
        TEXTURE_DOWNSAMPLE: 1,
        DENSITY_DISSIPATION: 0.98,
        VELOCITY_DISSIPATION: 0.99,
        PRESSURE_DISSIPATION: 0.8,
        PRESSURE_ITERATIONS: 25,
        CURL: 30,
        SPLAT_RADIUS: 0.005,
      };

      var pointers = [];
      var splatStack = [];
      var _getWebGLContext = getWebGLContext(canvas),
        gl = _getWebGLContext.gl,
        ext = _getWebGLContext.ext;

      function getWebGLContext(canvas) {
        var params = {
          alpha: false,
          depth: false,
          stencil: false,
          antialias: false,
        };

        var gl = canvas.getContext("webgl2", params);
        var isWebGL2 = !!gl;
        if (!isWebGL2)
          gl =
            canvas.getContext("webgl", params) ||
            canvas.getContext("experimental-webgl", params);

        var halfFloat = void 0;
        var supportLinearFiltering = void 0;
        if (isWebGL2) {
          gl.getExtension("EXT_color_buffer_float");
          supportLinearFiltering = gl.getExtension("OES_texture_float_linear");
        } else {
          halfFloat = gl.getExtension("OES_texture_half_float");
          supportLinearFiltering = gl.getExtension(
            "OES_texture_half_float_linear"
          );
        }

        gl.clearColor(0.0, 0.0, 0.0, 1.0);

        var halfFloatTexType = isWebGL2
          ? gl.HALF_FLOAT
          : halfFloat.HALF_FLOAT_OES;
        var formatRGBA = void 0;
        var formatRG = void 0;
        var formatR = void 0;

        if (isWebGL2) {
          formatRGBA = getSupportedFormat(
            gl,
            gl.RGBA16F,
            gl.RGBA,
            halfFloatTexType
          );
          formatRG = getSupportedFormat(gl, gl.RG16F, gl.RG, halfFloatTexType);
          formatR = getSupportedFormat(gl, gl.R16F, gl.RED, halfFloatTexType);
        } else {
          formatRGBA = getSupportedFormat(
            gl,
            gl.RGBA,
            gl.RGBA,
            halfFloatTexType
          );
          formatRG = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
          formatR = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
        }

        return {
          gl: gl,
          ext: {
            formatRGBA: formatRGBA,
            formatRG: formatRG,
            formatR: formatR,
            halfFloatTexType: halfFloatTexType,
            supportLinearFiltering: supportLinearFiltering,
          },
        };
      }

      function getSupportedFormat(gl, internalFormat, format, type) {
        if (!supportRenderTextureFormat(gl, internalFormat, format, type)) {
          switch (internalFormat) {
            case gl.R16F:
              return getSupportedFormat(gl, gl.RG16F, gl.RG, type);
            case gl.RG16F:
              return getSupportedFormat(gl, gl.RGBA16F, gl.RGBA, type);
            default:
              return null;
          }
        }

        return {
          internalFormat: internalFormat,
          format: format,
        };
      }

      function supportRenderTextureFormat(gl, internalFormat, format, type) {
        var texture = gl.createTexture();
        gl.bindTexture(gl.TEXTURE_2D, texture);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
        gl.texImage2D(
          gl.TEXTURE_2D,
          0,
          internalFormat,
          4,
          4,
          0,
          format,
          type,
          null
        );

        var fbo = gl.createFramebuffer();
        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
        gl.framebufferTexture2D(
          gl.FRAMEBUFFER,
          gl.COLOR_ATTACHMENT0,
          gl.TEXTURE_2D,
          texture,
          0
        );

        var status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
        if (status != gl.FRAMEBUFFER_COMPLETE) return false;
        return true;
      }

      function pointerPrototype() {
        this.id = -1;
        this.x = 0;
        this.y = 0;
        this.dx = 0;
        this.dy = 0;
        this.down = false;
        this.moved = false;
        this.color = [30, 0, 300];
      }

      pointers.push(new pointerPrototype());
      var GLProgram = (function () {
        function GLProgram(vertexShader, fragmentShader) {
          _classCallCheck(this, GLProgram);
          this.uniforms = {};
          this.program = gl.createProgram();

          gl.attachShader(this.program, vertexShader);
          gl.attachShader(this.program, fragmentShader);
          gl.linkProgram(this.program);

          if (!gl.getProgramParameter(this.program, gl.LINK_STATUS))
            throw gl.getProgramInfoLog(this.program);

          var uniformCount = gl.getProgramParameter(
            this.program,
            gl.ACTIVE_UNIFORMS
          );
          for (var i = 0; i < uniformCount; i++) {
            var uniformName = gl.getActiveUniform(this.program, i).name;
            this.uniforms[uniformName] = gl.getUniformLocation(
              this.program,
              uniformName
            );
          }
        }
        _createClass(GLProgram, [
          {
            key: "bind",
            value: function bind() {
              gl.useProgram(this.program);
            },
          },
        ]);
        return GLProgram;
      })();

      function compileShader(type, source) {
        var shader = gl.createShader(type);
        gl.shaderSource(shader, source);
        gl.compileShader(shader);

        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS))
          throw gl.getShaderInfoLog(shader);

        return shader;
      }

      var baseVertexShader = compileShader(
        gl.VERTEX_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    attribute vec2 aPosition;\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform vec2 texelSize;\n\n    void main () {\n        vUv = aPosition * 0.5 + 0.5;\n        vL = vUv - vec2(texelSize.x, 0.0);\n        vR = vUv + vec2(texelSize.x, 0.0);\n        vT = vUv + vec2(0.0, texelSize.y);\n        vB = vUv - vec2(0.0, texelSize.y);\n        gl_Position = vec4(aPosition, 0.0, 1.0);\n    }\n"
      );

      var clearShader = compileShader(
        gl.FRAGMENT_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    uniform sampler2D uTexture;\n    uniform float value;\n\n    void main () {\n        gl_FragColor = value * texture2D(uTexture, vUv);\n    }\n"
      );

      var displayShader = compileShader(
        gl.FRAGMENT_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    uniform sampler2D uTexture;\n\n    void main () {\n        gl_FragColor = texture2D(uTexture, vUv);\n    }\n"
      );

      var splatShader = compileShader(
        gl.FRAGMENT_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    uniform sampler2D uTarget;\n    uniform float aspectRatio;\n    uniform vec3 color;\n    uniform vec2 point;\n    uniform float radius;\n\n    void main () {\n        vec2 p = vUv - point.xy;\n        p.x *= aspectRatio;\n        vec3 splat = exp(-dot(p, p) / radius) * color;\n        vec3 base = texture2D(uTarget, vUv).xyz;\n        gl_FragColor = vec4(base + splat, 1.0);\n    }\n"
      );

      var advectionManualFilteringShader = compileShader(
        gl.FRAGMENT_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    uniform sampler2D uVelocity;\n    uniform sampler2D uSource;\n    uniform vec2 texelSize;\n    uniform float dt;\n    uniform float dissipation;\n\n    vec4 bilerp (in sampler2D sam, in vec2 p) {\n        vec4 st;\n        st.xy = floor(p - 0.5) + 0.5;\n        st.zw = st.xy + 1.0;\n        vec4 uv = st * texelSize.xyxy;\n        vec4 a = texture2D(sam, uv.xy);\n        vec4 b = texture2D(sam, uv.zy);\n        vec4 c = texture2D(sam, uv.xw);\n        vec4 d = texture2D(sam, uv.zw);\n        vec2 f = p - st.xy;\n        return mix(mix(a, b, f.x), mix(c, d, f.x), f.y);\n    }\n\n    void main () {\n        vec2 coord = gl_FragCoord.xy - dt * texture2D(uVelocity, vUv).xy;\n        gl_FragColor = dissipation * bilerp(uSource, coord);\n        gl_FragColor.a = 1.0;\n    }\n"
      );

      var advectionShader = compileShader(
        gl.FRAGMENT_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    uniform sampler2D uVelocity;\n    uniform sampler2D uSource;\n    uniform vec2 texelSize;\n    uniform float dt;\n    uniform float dissipation;\n\n    void main () {\n        vec2 coord = vUv - dt * texture2D(uVelocity, vUv).xy * texelSize;\n        gl_FragColor = dissipation * texture2D(uSource, coord);\n        gl_FragColor.a = 1.0;\n    }\n"
      );

      var divergenceShader = compileShader(
        gl.FRAGMENT_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uVelocity;\n\n    vec2 sampleVelocity (in vec2 uv) {\n        vec2 multiplier = vec2(1.0, 1.0);\n        if (uv.x < 0.0) { uv.x = 0.0; multiplier.x = -1.0; }\n        if (uv.x > 1.0) { uv.x = 1.0; multiplier.x = -1.0; }\n        if (uv.y < 0.0) { uv.y = 0.0; multiplier.y = -1.0; }\n        if (uv.y > 1.0) { uv.y = 1.0; multiplier.y = -1.0; }\n        return multiplier * texture2D(uVelocity, uv).xy;\n    }\n\n    void main () {\n        float L = sampleVelocity(vL).x;\n        float R = sampleVelocity(vR).x;\n        float T = sampleVelocity(vT).y;\n        float B = sampleVelocity(vB).y;\n        float div = 0.5 * (R - L + T - B);\n        gl_FragColor = vec4(div, 0.0, 0.0, 1.0);\n    }\n"
      );

      var curlShader = compileShader(
        gl.FRAGMENT_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uVelocity;\n\n    void main () {\n        float L = texture2D(uVelocity, vL).y;\n        float R = texture2D(uVelocity, vR).y;\n        float T = texture2D(uVelocity, vT).x;\n        float B = texture2D(uVelocity, vB).x;\n        float vorticity = R - L - T + B;\n        gl_FragColor = vec4(vorticity, 0.0, 0.0, 1.0);\n    }\n"
      );

      var vorticityShader = compileShader(
        gl.FRAGMENT_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uVelocity;\n    uniform sampler2D uCurl;\n    uniform float curl;\n    uniform float dt;\n\n    void main () {\n        float T = texture2D(uCurl, vT).x;\n        float B = texture2D(uCurl, vB).x;\n        float C = texture2D(uCurl, vUv).x;\n        vec2 force = vec2(abs(T) - abs(B), 0.0);\n        force *= 1.0 / length(force + 0.00001) * curl * C;\n        vec2 vel = texture2D(uVelocity, vUv).xy;\n        gl_FragColor = vec4(vel + force * dt, 0.0, 1.0);\n    }\n"
      );

      var pressureShader = compileShader(
        gl.FRAGMENT_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uPressure;\n    uniform sampler2D uDivergence;\n\n    vec2 boundary (in vec2 uv) {\n        uv = min(max(uv, 0.0), 1.0);\n        return uv;\n    }\n\n    void main () {\n        float L = texture2D(uPressure, boundary(vL)).x;\n        float R = texture2D(uPressure, boundary(vR)).x;\n        float T = texture2D(uPressure, boundary(vT)).x;\n        float B = texture2D(uPressure, boundary(vB)).x;\n        float C = texture2D(uPressure, vUv).x;\n        float divergence = texture2D(uDivergence, vUv).x;\n        float pressure = (L + R + B + T - divergence) * 0.25;\n        gl_FragColor = vec4(pressure, 0.0, 0.0, 1.0);\n    }\n"
      );

      var gradientSubtractShader = compileShader(
        gl.FRAGMENT_SHADER,
        "\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uPressure;\n    uniform sampler2D uVelocity;\n\n    vec2 boundary (in vec2 uv) {\n        uv = min(max(uv, 0.0), 1.0);\n        return uv;\n    }\n\n    void main () {\n        float L = texture2D(uPressure, boundary(vL)).x;\n        float R = texture2D(uPressure, boundary(vR)).x;\n        float T = texture2D(uPressure, boundary(vT)).x;\n        float B = texture2D(uPressure, boundary(vB)).x;\n        vec2 velocity = texture2D(uVelocity, vUv).xy;\n        velocity.xy -= vec2(R - L, T - B);\n        gl_FragColor = vec4(velocity, 0.0, 1.0);\n    }\n"
      );

      var textureWidth = void 0;
      var textureHeight = void 0;
      var density = void 0;
      var velocity = void 0;
      var divergence = void 0;
      var curl = void 0;
      var pressure = void 0;
      initFramebuffers();

      var clearProgram = new GLProgram(baseVertexShader, clearShader);
      var displayProgram = new GLProgram(baseVertexShader, displayShader);
      var splatProgram = new GLProgram(baseVertexShader, splatShader);
      var advectionProgram = new GLProgram(
        baseVertexShader,
        ext.supportLinearFiltering
          ? advectionShader
          : advectionManualFilteringShader
      );
      var divergenceProgram = new GLProgram(baseVertexShader, divergenceShader);
      var curlProgram = new GLProgram(baseVertexShader, curlShader);
      var vorticityProgram = new GLProgram(baseVertexShader, vorticityShader);
      var pressureProgram = new GLProgram(baseVertexShader, pressureShader);
      var gradienSubtractProgram = new GLProgram(
        baseVertexShader,
        gradientSubtractShader
      );

      function initFramebuffers() {
        textureWidth = gl.drawingBufferWidth >> config.TEXTURE_DOWNSAMPLE;
        textureHeight = gl.drawingBufferHeight >> config.TEXTURE_DOWNSAMPLE;

        var texType = ext.halfFloatTexType;
        var rgba = ext.formatRGBA;
        var rg = ext.formatRG;
        var r = ext.formatR;

        density = createDoubleFBO(
          2,
          textureWidth,
          textureHeight,
          rgba.internalFormat,
          rgba.format,
          texType,
          ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST
        );
        velocity = createDoubleFBO(
          0,
          textureWidth,
          textureHeight,
          rg.internalFormat,
          rg.format,
          texType,
          ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST
        );
        divergence = createFBO(
          4,
          textureWidth,
          textureHeight,
          r.internalFormat,
          r.format,
          texType,
          gl.NEAREST
        );
        curl = createFBO(
          5,
          textureWidth,
          textureHeight,
          r.internalFormat,
          r.format,
          texType,
          gl.NEAREST
        );
        pressure = createDoubleFBO(
          6,
          textureWidth,
          textureHeight,
          r.internalFormat,
          r.format,
          texType,
          gl.NEAREST
        );
      }

      function createFBO(texId, w, h, internalFormat, format, type, param) {
        gl.activeTexture(gl.TEXTURE0 + texId);
        var texture = gl.createTexture();
        gl.bindTexture(gl.TEXTURE_2D, texture);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, param);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, param);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
        gl.texImage2D(
          gl.TEXTURE_2D,
          0,
          internalFormat,
          w,
          h,
          0,
          format,
          type,
          null
        );

        var fbo = gl.createFramebuffer();
        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
        gl.framebufferTexture2D(
          gl.FRAMEBUFFER,
          gl.COLOR_ATTACHMENT0,
          gl.TEXTURE_2D,
          texture,
          0
        );
        gl.viewport(0, 0, w, h);
        gl.clear(gl.COLOR_BUFFER_BIT);

        return [texture, fbo, texId];
      }

      function createDoubleFBO(
        texId,
        w,
        h,
        internalFormat,
        format,
        type,
        param
      ) {
        var fbo1 = createFBO(texId, w, h, internalFormat, format, type, param);
        var fbo2 = createFBO(
          texId + 1,
          w,
          h,
          internalFormat,
          format,
          type,
          param
        );

        return {
          get read() {
            return fbo1;
          },
          get write() {
            return fbo2;
          },
          swap: function swap() {
            var temp = fbo1;
            fbo1 = fbo2;
            fbo2 = temp;
          },
        };
      }

      var blit = (function () {
        gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
        gl.bufferData(
          gl.ARRAY_BUFFER,
          new Float32Array([-1, -1, -1, 1, 1, 1, 1, -1]),
          gl.STATIC_DRAW
        );
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, gl.createBuffer());
        gl.bufferData(
          gl.ELEMENT_ARRAY_BUFFER,
          new Uint16Array([0, 1, 2, 0, 2, 3]),
          gl.STATIC_DRAW
        );
        gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
        gl.enableVertexAttribArray(0);

        return function (destination) {
          gl.bindFramebuffer(gl.FRAMEBUFFER, destination);
          gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
        };
      })();

      var lastTime = Date.now();
      multipleSplats(parseInt(Math.random() * 20) + 5);
      update();

      function update() {
        resizeCanvas();

        var dt = Math.min((Date.now() - lastTime) / 1000, 0.016);
        lastTime = Date.now();

        gl.viewport(0, 0, textureWidth, textureHeight);

        if (splatStack.length > 0) multipleSplats(splatStack.pop());

        advectionProgram.bind();
        gl.uniform2f(
          advectionProgram.uniforms.texelSize,
          1.0 / textureWidth,
          1.0 / textureHeight
        );
        gl.uniform1i(advectionProgram.uniforms.uVelocity, velocity.read[2]);
        gl.uniform1i(advectionProgram.uniforms.uSource, velocity.read[2]);
        gl.uniform1f(advectionProgram.uniforms.dt, dt);
        gl.uniform1f(
          advectionProgram.uniforms.dissipation,
          config.VELOCITY_DISSIPATION
        );
        blit(velocity.write[1]);
        velocity.swap();

        gl.uniform1i(advectionProgram.uniforms.uVelocity, velocity.read[2]);
        gl.uniform1i(advectionProgram.uniforms.uSource, density.read[2]);
        gl.uniform1f(
          advectionProgram.uniforms.dissipation,
          config.DENSITY_DISSIPATION
        );
        blit(density.write[1]);
        density.swap();

        for (var i = 0; i < pointers.length; i++) {
          var pointer = pointers[i];
          if (pointer.moved) {
            splat(pointer.x, pointer.y, pointer.dx, pointer.dy, pointer.color);
            pointer.moved = false;
          }
        }

        curlProgram.bind();
        gl.uniform2f(
          curlProgram.uniforms.texelSize,
          1.0 / textureWidth,
          1.0 / textureHeight
        );
        gl.uniform1i(curlProgram.uniforms.uVelocity, velocity.read[2]);
        blit(curl[1]);

        vorticityProgram.bind();
        gl.uniform2f(
          vorticityProgram.uniforms.texelSize,
          1.0 / textureWidth,
          1.0 / textureHeight
        );
        gl.uniform1i(vorticityProgram.uniforms.uVelocity, velocity.read[2]);
        gl.uniform1i(vorticityProgram.uniforms.uCurl, curl[2]);
        gl.uniform1f(vorticityProgram.uniforms.curl, config.CURL);
        gl.uniform1f(vorticityProgram.uniforms.dt, dt);
        blit(velocity.write[1]);
        velocity.swap();

        divergenceProgram.bind();
        gl.uniform2f(
          divergenceProgram.uniforms.texelSize,
          1.0 / textureWidth,
          1.0 / textureHeight
        );
        gl.uniform1i(divergenceProgram.uniforms.uVelocity, velocity.read[2]);
        blit(divergence[1]);

        clearProgram.bind();
        var pressureTexId = pressure.read[2];
        gl.activeTexture(gl.TEXTURE0 + pressureTexId);
        gl.bindTexture(gl.TEXTURE_2D, pressure.read[0]);
        gl.uniform1i(clearProgram.uniforms.uTexture, pressureTexId);
        gl.uniform1f(clearProgram.uniforms.value, config.PRESSURE_DISSIPATION);
        blit(pressure.write[1]);
        pressure.swap();

        pressureProgram.bind();
        gl.uniform2f(
          pressureProgram.uniforms.texelSize,
          1.0 / textureWidth,
          1.0 / textureHeight
        );
        gl.uniform1i(pressureProgram.uniforms.uDivergence, divergence[2]);
        pressureTexId = pressure.read[2];
        gl.uniform1i(pressureProgram.uniforms.uPressure, pressureTexId);
        gl.activeTexture(gl.TEXTURE0 + pressureTexId);
        for (var _i = 0; _i < config.PRESSURE_ITERATIONS; _i++) {
          gl.bindTexture(gl.TEXTURE_2D, pressure.read[0]);
          blit(pressure.write[1]);
          pressure.swap();
        }

        gradienSubtractProgram.bind();
        gl.uniform2f(
          gradienSubtractProgram.uniforms.texelSize,
          1.0 / textureWidth,
          1.0 / textureHeight
        );
        gl.uniform1i(
          gradienSubtractProgram.uniforms.uPressure,
          pressure.read[2]
        );
        gl.uniform1i(
          gradienSubtractProgram.uniforms.uVelocity,
          velocity.read[2]
        );
        blit(velocity.write[1]);
        velocity.swap();

        gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
        displayProgram.bind();
        gl.uniform1i(displayProgram.uniforms.uTexture, density.read[2]);
        blit(null);

        requestAnimationFrame(update);
      }

      function splat(x, y, dx, dy, color) {
        splatProgram.bind();
        gl.uniform1i(splatProgram.uniforms.uTarget, velocity.read[2]);
        gl.uniform1f(
          splatProgram.uniforms.aspectRatio,
          canvas.width / canvas.height
        );
        gl.uniform2f(
          splatProgram.uniforms.point,
          x / canvas.width,
          1.0 - y / canvas.height
        );
        gl.uniform3f(splatProgram.uniforms.color, dx, -dy, 1.0);
        gl.uniform1f(splatProgram.uniforms.radius, config.SPLAT_RADIUS);
        blit(velocity.write[1]);
        velocity.swap();

        gl.uniform1i(splatProgram.uniforms.uTarget, density.read[2]);
        gl.uniform3f(
          splatProgram.uniforms.color,
          color[0] * 0.3,
          color[1] * 0.3,
          color[2] * 0.3
        );
        blit(density.write[1]);
        density.swap();
      }

      function multipleSplats(amount) {
        for (var i = 0; i < amount; i++) {
          var color = [
            Math.random() * 10,
            Math.random() * 10,
            Math.random() * 10,
          ];
          var x = canvas.width * Math.random();
          var y = canvas.height * Math.random();
          var dx = 1000 * (Math.random() - 0.5);
          var dy = 1000 * (Math.random() - 0.5);
          splat(x, y, dx, dy, color);
        }
      }

      function resizeCanvas() {
        if (
          canvas.width != canvas.clientWidth ||
          canvas.height != canvas.clientHeight
        ) {
          canvas.width = canvas.clientWidth;
          canvas.height = canvas.clientHeight;
          initFramebuffers();
        }
      }

      canvas.addEventListener("mousemove", function (e) {
        pointers[0].moved = pointers[0].down;
        pointers[0].dx = (e.offsetX - pointers[0].x) * 10.0;
        pointers[0].dy = (e.offsetY - pointers[0].y) * 10.0;
        pointers[0].x = e.offsetX;
        pointers[0].y = e.offsetY;
      });

      canvas.addEventListener(
        "touchmove",
        function (e) {
          e.preventDefault();
          var touches = e.targetTouches;
          for (var i = 0; i < touches.length; i++) {
            var pointer = pointers[i];
            pointer.moved = pointer.down;
            pointer.dx = (touches[i].pageX - pointer.x) * 10.0;
            pointer.dy = (touches[i].pageY - pointer.y) * 10.0;
            pointer.x = touches[i].pageX;
            pointer.y = touches[i].pageY;
          }
        },
        false
      );

      canvas.addEventListener("mousedown", function () {
        pointers[0].down = true;
        pointers[0].color = [
          Math.random() + 0.2,
          Math.random() + 0.2,
          Math.random() + 0.2,
        ];
      });

      canvas.addEventListener("touchstart", function (e) {
        e.preventDefault();
        var touches = e.targetTouches;
        for (var i = 0; i < touches.length; i++) {
          if (i >= pointers.length) pointers.push(new pointerPrototype());

          pointers[i].id = touches[i].identifier;
          pointers[i].down = true;
          pointers[i].x = touches[i].pageX;
          pointers[i].y = touches[i].pageY;
          pointers[i].color = [
            Math.random() + 0.2,
            Math.random() + 0.2,
            Math.random() + 0.2,
          ];
        }
      });

      window.addEventListener("mouseup", function () {
        pointers[0].down = false;
      });

      window.addEventListener("touchend", function (e) {
        var touches = e.changedTouches;
        for (var i = 0; i < touches.length; i++) {
          for (var j = 0; j < pointers.length; j++) {
            if (touches[i].identifier == pointers[j].id)
              pointers[j].down = false;
          }
        }
      });
    },
  },
};
</script>

<style lang="scss" scoped>
.liquid-effect {
  height: 100%;
}
</style>

<style lang="scss">
html,
body {
  overflow: hidden;
}

body {
  margin: 0;
  position: absolute;
  width: 100%;
  height: 100%;
}

canvas {
  width: 100%;
  height: 100%;
}
</style>